Among the many herbicidal compounds commercially available, the thiocarbamates alone or admixed with other herbicides, such as the triazines, have reached a relatively high degree of commercial success. These herbicides are immediately toxic to a large number of weed pests at different concentrations varying with the resistance of the weed pests. Some examples of these compounds are described and claimed in U.S. Pat. Nos. 2,913,327, 3,037,853, 3,175,897, 3,185,720, 3,198,786 and 3,582,314. It has been found in practice that the use of these thiocarbamates as herbicides on crops sometimes causes serious injuries to the crop plant. When used in the recommended amounts in the soil to control many broadleaf weeds and grasses, serious malformation and stunting of the crop plants result. This abnormal growth in the crop plants results in loss of crop yield. Previous attempts to overcome this problem involves the treatment of the crop seed with certain antagonistic agents prior to planting, see U.S. Pat. Nos. 3,131,509 and 3,564,768. These antagonistic agents have not been notably successful. The aforementioned patent specifically exemplifies the treatment of seeds employing compounds of a different chemical class not suggestive of the present invention.
Other preferred herbicidal compounds whose effect can be modified by the instant compounds include the acetanilides, such as 2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide and the urea-type herbicides, such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea.